Aug. 3 11:45 AM PT12:45 PM MT1:45 PM CT2:45 PM ET18:45 GMT2:45 AM 北京时间11:45 AM MST1:45 PM EST1:45 PM CT22:45 UAE14:45 ET17:45 - The Atlanta Falcons have added depth at safety by signing free agent Tyrell Johnson. Analysis: Sunday's move comes after safety Dwight Lowery left Friday night's scrimmage with a concussion. Lowery missed most of the 2013 season with Jacksonville after suffering a concussion at Seattle on Sept. 22. He later was placed on injured reserve and released. Johnson, a second-round pick by Minnesota in 2008, played four seasons with the Vikings. He played four games with Detroit in 2012.